Vacuum-tube filament fuse



Sept. 22, 1925. 1,554,499 w. HEALEY ET AL VACUUM TUBE FILAMENT FUSE Filed April 17, 1924` IN VEN TOR A TTORNE YS l 1,554,499 PATENT oFFlcE. i

WESLEY HEALEY .AND MI JULIAN ROQUIER, 0F WAUKEG-AN, ILLINOIS.

'VACUUM-TUBE FILAMENT FUSE.

Application led April 17, 1924. Serial No. 707,166.

To all whom. it may concern:

Be it known that we, WESLEY HEALEY and M JULIAN ROQUIER, both citizens of the United States, and residents of Waukegan, county of Lake, State of Illinois, have pinvented a new and useful Improvement in Vacuum-Tube Filament Fuses, of which the following is a full, clear, and exact description.

Our invention relates to improvements in vacuum tube filament fuses, for use with radio vacuum tubes and the like, and it consists in the combinations, constructions, and arrangements herein described and claimed.

An object of the invention is to .provide a device of the type desc-ribed in which the fuse forms a part of an adaptor for receiving the standard radio vacuum tube, and which adaptor is arranged to be disposed in the ordinary type of vacuum tube socket. This construction makes it possible to quickly remove the entire device, should the fuse disintegrate with lexcessive current, and permit the installation -of a new adaptor having a fresh fuse element therein. The

vfuse which has been blown may now be replaced with a new one and the first device laid aside, ready for use.v It will be apparent from this novel construction that the operator need not be held up in its work by the blowing of' a fuse which advantage is especially important in commercial radio stations.

A further object of the invention is to l provide a' device of the type described in which the fusible element is disposed in a vacuumized tube and in which the fuse is incandescent during the operation of the tube to a point near disintegrating condition, so that any slight increase in filament current which might tend to harm the tube filament will cause the fuse to disintegrate and thus spare the tube filament. v

A further object of our invention `is to -provide a device of the type described,

which is extremely simple in construction, which is compact in form, and which is thoroughly practical commercially.

Other objects and advantages will appear in the following specification, and the novel features of the invention will be particularly pointed out in the appended claims.

Our invention is illustrated in the accompanying drawings, forming part of this application in which- Figure 1 is a sectional view of an embodiment of our invention, and

Figure 2 is an enlarged sectional view of a part of the mechanism shown in Figure 1, including-the fusible element.

In carrying out our invention we make use of a tubular casing 1 having a partition wall 2 of insulating material transversely disposed thereiny at substantially the mid point of the casing, thereby dividing the casing into two parts. The casing 1 is slightly larger in diameter above the partition wall 2, than that portion below thepartition. Y

The portion of the tubular casing 1 above the partition 2 has a bayonet slot 3 in the upper edge thereof for receiving a pin 4 carried by the standard base` 5 of the radio vacuum tube 6. The casing 1 is provided with an insulating partition 7 at its lowermost end arranged so as to-close that end and thus form a base portion which may be inserted in the ordinary type of vacuum tube receptacle socket normally employed for the reception of tubes having base members such as the base member 5. A

Three conductors 8 are projected through the partition Walls 7 and 2 and held in place b-y binding nuts 9. The conductors 8 are arranged to depend below the lower surface of the partition wall 7 so as to engage with the contact members pro-vided in the ordi v 'extend through the partition walls 7 and 2 on a vertical axis and therefore their depending portions below the partition wall 7 must contact with the proper contact members forming part of the standard tube receptacle provided the base portion or lower part of the member 1 is properly disposed in the vacuum tube receptacle.

The remaining filament terminal 11 of the base 5 is arranged to engage with the contact member 12 carried b a conductor 13, (see Figure 2). This con uctor 13 extends for a short distance below the partition 2 and is ductorl. The purpose of the spring clips 14C and 18 is to support opposite ends 19 and 20 ofa fuse element, generally indicated at 21. This fuse element consists of a sealed tube 22 preferably of glass. Prior to mounting the tube 22 on its supporting end portions 19 and 20, the air is exhausted therefrom so that the tube may not support com'- bustion therein. .A fuse 23' of tungsten or other suitable material capable of retaining its form while incandescent is disposed Within the tube 22 and has its opposite ends connected with the end portions 19 and 20 of the fuse element heretofore described.

This tungstenfuse element 23 is of such diameter and resistance as to be heated by I2R, loss resulting from the current flowing through the filament of the tube 6. The dimensions of the fuse; 23 are such that the heat created in it by its 12R loss brings the fuse to a near disintegrating condition. Just how near to the disintegrating condition this fuse 23 is brought depends upon the safety factor required Which may be determined by study of the characteristics of the filament employed in the tube 6.

-From the foregoing description of the p various parts of the device, -the operation thereof may be readily understood. In employing my improved vacuum tube filament fuse, the tube 6 is removed from its standard socket and the lower portion of the tubular member 1 is placed in the socket, so that the depending portions of the conductors-8 and 15 engage with the contact members provided in the standard socket. This type of socket is Well known and extensively used in the art.

( Thebase 5 of the. vacuum tube G is then inserted in the upper portion of the tubular member 1 so that the pin 4 is received in the bayonet slot 3. The contact members de pending from the base 5 will engage with excessffiow, the current Will non7 cause the' fuse 23 to disintegrate and thus save damage to the filament of the tube. In the event of disintegration of the fuse anew device may be quickly lsubstituted for the one in use, While. a new fuse 21 is disposed in the clips 14 and 18 of the conductors 13 and 15.

We claim:

1. A. vacuum tube filament fuse of the type described comprising a vreceptacle for re ceiving the base of a vacuum tube, a plug base associated with said receptacle, conductors for connecting said receptacle with said plugbase, and a vacuumized fuse element connected in series with one of said conductors arranged for the conduction of current to the lament: of said Vacuum tube, Said fuse lbeing constructed so as to maintain a condition near disintegration when the current for said flamentis passing therethrough. l

2. In a device of the character described, a vacuum tube filament fuse comprising a sealed tube from which the air has been exlia-usted, a fuse element disposed Within said tube and means extending exteriorly of the tube at each end and connected with the opposite ends of the fuse respectively for facilitating electrical connections to the fuse, said fuse being constructed so as to remain incandescent and in a condition near disintegration when current sufficient for the operation of the vacuum' tube filament is passed therethrough.

WESLEY HEALEY. M JULIAN ROQUIER. 

